Compression technology is used in the field of wireless communication etc. in order to implement the transmission of speech and video signals in real time. Vector quantization technology is an effective method for compressing speech and video data.
In patent document 1, technology is disclosed that makes broadband speech signals from narrowband speech signals using vector quantization technology. In patent document 1, results of LPC analysis on input narrowband speech signals are vector-quantized using a narrowband codebook, the vectors are then decoded using a broadband codebook, and the resulting code is subjected to LPC synthesis so as to obtain a broadband speech signal.
Patent Document 1: Japanese Patent Application Laid-Open No. Hei. 6-118995.